1. Technical Field
Various embodiments relate to a semiconductor integrated circuit, and more particularly, to an arrangement structure of transistors constituting a differential amplifier and a method of arranging the transistors.
2. Related Art
In general, a differential amplifier has been applied to various fields of a semiconductor integrated circuit.
For example, a differential amplifier is mainly used in an internal voltage generation circuit which receives an external voltage and converts the received voltage into an internal voltage having a predetermined level. In addition, the differential amplifier is used in various fields such as a data output buffer and a comparator circuit.
Referring to FIG. 1, the differential amplifier 10 may include a first transistor TR1 configured to receive a first input voltage Vin1 and a second transistor TR2 configured to receive a second input voltage Vin2. The drain of the first transistor TR1 and the drain of the second transistor TR2 are electrically coupled to a power supply voltage VDD, and the source of the first transistor TR1 and the source of the second transistor TR2 are electrically coupled to a current source CS coupled to a ground voltage terminal. In FIG. 1, R1 represents a voltage drop resistor coupled between the first transistor TR1 and the power supply voltage terminal, and R2 represents a voltage drop resistor coupled between the second transistor TR2 and the power supply voltage terminal.
The first and second transistors TR1 and TR2 constituting the differential amplifier 10 are required to have the same performance, in order to accurately compare input voltages Vin1 and Vin2. Thus, the transistors TR1 and TR2 must be formed to have the same size and shape. In order to reduce a difference between the first and second transistors TR1 and TR2 when the transistors TR1 and TR2 are integrated in a semiconductor substrate, one transistor may be divided into a plurality of transistors so that the plurality of transistors has a fingered structure (hereinafter, a plurality of segment transistors). The segment transistor of the first transistors TR1 and the segment transistor of the second transistor TR2 may be alternately arranged to compensate for the mismatches between the first and second transistors TR1 and TR2.
Referring to FIG. 2, when the differential amplifier structure is substituted for “a regular stress variation curve for distance change” and then simulated, the stress variations of the first and second transistors TR1 and TR2 are substantially similar to each other.
However, when the transistor TR1 and TR2 is divided into the plurality of segment transistors, a distance between the signal input terminal and a first fingered segment transistor constituting the first or second transistor TR1 or TR2 may be different from a distance between the signal input terminal and the first or second transistor TR1 or TR2 which does not divide into the plurality of fingered segment transistors.
When the transistor structure is substituted for “an irregular stress variation curve for distance change” which is calculated based on such a principle and then simulated as illustrated in FIG. 3, a difference occurs between stress variations of the first and second transistors TR1 and TR2.
Thus, as the transistors of the differential amplifier which must have substantially the same performance exhibit different performances, it is impossible to acquire reliable differential amplification efficiency.